Liquid-filled fuse cutout having a fuse carrier with unique mounting and support features



Aug. 11, 1970 E, A. VRABEL 3,524,158

' LIQUID FILLED FUSE'CUTOUT HAVING 'A FUSE CARRIER WITH UNIQUE MOUNTING AND SUPPORT FEATURES Filed May 16, 1969 2 Shecis-S'neet 'l 3,524,158 ARRIER 2 Sheets- Sheet "2 W 7 ||l1IIIFM4ImmWUH| ND SUPPORT FEATURES M 1, .v f

E.,A. VRABEL Aug. 11, 1970 LIQUID FILLED FUSE CUTOUT HAVING A FUSE C WITH UNIQUE MOUNTING A Filed May 16, 1969 United States Patent O 3,524,158 LIQUID-FILLED FUSE CUTOUT HAVING A FUSE CARRIER WITH UNIQUE MDUNTING AND SUP- PORT FEATURES Edward A. Vrabel, Pittsfield, Mass., assigner to General Electric Company, a corporation of New York File/.l May 16, 1969, Ser. No. 825,136 Int. Cl. yIlltllh 85/14 U.S. Cl. 337-204 Claims ABSTRACT OF THE DISCLSURE A fluid filled circuit interrupter having a fuse supported by a fuse carrier which is characterized by having structural features that protect the fuse carrier from damage due to rapid circulation of liquid in the interrupter in response to fusion of the fuse. These unique structural features include a glass sleeve embedded in the fuse carrier adjacent its support, and liquid flow control means that deliect high-pressure circulating liquid away from critical contactsupporting portions of the fuse carrier.

This invention relates to liquid illed cutouts and more particularly to oil filled fuse cutouts having a combination fuse carrier and contact supporting member mounted therein in a manner such that it is subjected to liquid flowing under very high pressures when a fuse fails within the cutout housing.

Present day liquid filled fuse cutouts commonly comprise an oil lled steel container housing a pair of manually-operable switches that function to open an electric circuit between two spaced-apart bushings through which power cables transmit electric power to and from the cut- Out. In addition, such cutouts normally include a fuse that is series connected with the circuit through the cutout to protect it from damage due to excess overcurrent. When a fuse ruptures in such a cutout the cutout container and the components mounted in it are subjected to very high pressures created by the generation of arc gases in the oil of the cutout. It has been found that a relatively thin steel container will safely withstand such pressures, however, operating components mounted within the container are frequently damaged when a large overcurrent fault is interrupted by a fuse failure. Thus, the current interrupting rating of an oil filled cutout is a function both of the interrupting rating of the fuse mounted within the cutout and of the ability of the component parts of the cutout to withstand the high pressures developed within the oil when the fuse ruptures.

Of course, it is possible to increase the ability of an oil filled cutout to interrupt high currents without damage to its internal component parts by simply making such parts larger and, thus, stronger or by making the parts of materials having higher tensile strength. However, these expedients are generally undesirable because they increase manufacturing costs and they may make the cutout undesirably large in relation to the relatively small vaults and metal clad housings in which most such cutouts are now utilized.

From the foregoing discussion it can be seen that it is desirable to increase the safe interrupting rating of oil filled, fused cutouts without either increasing their overall size or their cost.

It is, therefore, one object of this invention to provide a liquid-filled, fused cutout in which means are provided to prevent damage being done to the internal components of the cutout by liquid that is rapidly circulated therein in response to a fuse blowing.

Another object of the invention is to provide an oil filled, fused cutout with a fuse carrier having contact ICC mounting shoulders that are streamlined to dellect circulating oil away from the shoulders and, thus, prevent them from being damaged by high pressure oil impinging on their surfaces.

A further object of the invention is to provide an oil filled, fused cutout having a fuse carrier support means that is inexpensively reinforced to prevent it from being damaged when high pressure oil circulates within the cutout housing.

In one preferred form of the invention a liquid filled, fused cutout is provided with an elongated fuse carrier having a pair of contact-mounting shoulders thereon that are protected from damage due to high pressure circulating oil by having oil deflecting, sloped surfaces disposed between the shoulders and the elongated body portion of the fuse carrier to dellect oil away from the shoulders. The fuse carrier is also provided with an embedded glass sleeve having a passageway through it for a pin that is rigidly mounted in a support on one Wall of the cutout. The glass sleeve is effective to prevent the fuse carrier from being broken in tension when high pressure liquid is circulated within the cutout housing.

The features of this invention which are believed to be novel are set forth with particularity in the claims appended hereto. The invention itself, as well as the manner in which the various objects thereof are carried out, will be better understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. l is a side elevation, partly in cross section of a liquid filled, fused cutout assembly made in accordance with a preferred embodiment of the invention.

FIG. 2 is a side elevation of a fuse carrier, showing component parts thereof in phantom, of the type ernbodied in the fuse cutout illustrated in FIG. l of the drawing.

Referring now to FIG. l of the drawing, there is shown a liquid filled cutout 1 having a drawn steel container 2 that is threaded into a cast-iron cover 3 and that is provided with a drain plug 4 at its lower end. The interior of the cutout 1 is vented through top cover S of a fuse carrier support means that is mounted on and sealed in any suitable conventional manner to the top of the cutout cover 3. The lower portion of the support means 5 is shown in cross section at 5a and a pin 6 is positioned in two oppositely facing apertures in this extended portion of the support means 5. An elongated fuse carrier 7 formed of rn-oldable epoxy material, or other suitable electrical insulating material such as wood, is suspended from the pin 6 in a predetermined relatively fixed position within the housing 1. The fuse carrier 7 has an elongated body portion 8 and a pair of shoulders 9 and 10 projecting laterally therefrom.

As can be seen in FIG. 2 of the drawings, the shoulders 9 and 10 respectively support a pair of contacts 11 and 12 that are locked in position with respect to the shoulders by a pair of threaded nuts 13 and 14 that threadably engage shank portions 11a and 12a of these contacts. It will be understood that more than one threaded shank portion and locking nut may be utilized to secure the contacts if desired in some embodiments of the invention. Referring again to FIG. 1 of the drawing in order to complete a description of the basic functional component parts of the cutout 1, it will be understood that when the contacts 11 and 12 are in operating position they engage cooperating contacts that form part of an electrical circuit through the cutout. One such contact is designated by the numeral 15, and these contacts are connected, respectively, to the power conductors 16 and 17 through which electric power is transmitted to and from the cutout 1. Of course these conductors 16 and 17 are suitably insulated by bushings 18 and 19 that are mounted in any conventional maner in the cast iron cover 3 of the cutouts. Electrically connected in series with the contacts 11 and 12 by resilient links 20 and 21 is a fuse 22 that is adapted to rupture when a predetermined excess current passes through it thereby to interrupt the circuit formed between the conductors 16 and 17.

It will be understood by those skilled in the art that the mechanical strength of the drawn steel container 2 and the cast iron cover 3 is much greater than necessary to withstand the internal pressures that are developed when the fuse 22 ruptures and causes an arc that generates gas within the container 2. The purpose of the present invention is to provide a fuse carrier such as the fuse carrier 7 that is capable of withstanding much higher pressure than was heretofore possible with conventional fuse carriers without being damaged when the fuse 22 ruptures.

It will be understood that'when the fuse 22 ruptures, an arc is formed between the resilient links 20 and 21 and this arc suddenly generates a substantial volume of gas that forces the insulating liquid 23 within the container to circulate rapidly through the various passages around the component parts of the cutout confined within container 2. Since such a gas volume is initially formed near the bottom of container 2, the gases force the oil 23 to circulate rapidly toward the top of the cover 3, with most of the oil flowing upward adjacent the walls of the container 2 and then flowing downward generally parallel to the longitudinal portion 8 of fuse carrier 1 back toward the bottom of container 2. By a careful study of the action of oil 23 under such gas-generated conditions, it has been found that in prior are devices very high pressures are created on the shoulders 9 and 10 of the fuse carrier 7 due to circulating oil flowing through the apertures 24 in the extension a of fuse carrier support means 5. Thus, as noted above, design limitation of prior art cutout interrupting ratings was found to be the ability of contact supporting shoulders such as 9 and 10 to withstand this shearing force of the circulating fiuid caused by arcgenerated gases. It should be noted that in addition to providing a means for mounting contacts 11 and 12, shoulders such as 9 and 10 are necessary on the fuse carrier 7 to keep it properly aligned when the carrier is placed into the cutout so contacts 11 and 12 do not inadvertently hit the fixed contacts 15.

With the unique fuse carrier construction of the present invention it has been discovered that it is possible to increase the interrupting current rating of an oil fused cutout aproximately 50% by protecting the shoulders 9 and 10 of fuse carrier 7 from the high pressures caused by circulating oils tending to impinge thereon. This protection is provided by streamlining means 9a and a in the from of a pair of bodies of moldable epoxy material that are shaped to form sloped surfaces extending between the body portion 8 and the upper surfaces of shoulders 9 and 10. An example of an epoxy material suitable for forming the streamlining means 9a and 10a is an epoxy resin adhesive commercially known as Hysol Corporations 2038. This material can be purchased by brand name from Hysol Corp. without detailed specification. In order to cure this Hysol 2038 resin, a curing agent, such as Hysol Corps Hardener 3475 can be mixed with it in a ratio of one part hardener to 4 parts adhesive. In a preferred form of the invention the sloped surfaces of body portions 9a and 10a form an angle of approximately 45 with respect to the longitudinal axis of the fuse carrier 7; however, it has been found that such sloped surfaces provide adequate protection for the shoulders 9 and 10 to allow a substantial safe interrupting rating increase when these surfaces form an angle in excess of 25 with respect to the longitudinal axis of fuse carrier 7.

In order to forni the sloped surfaces 9a and 10a of the invention in the preferred embodiment thereof, the self-curing moldable epoxy material is used to lill the cavities 25 and 26 (see FIG. 2) though which the nuts 13 and 14 are fastened to the contact-supporting Shanks 11a and 12a to secure the contacts 11 and 12 in predetermined positions on the fuse carrier 7. This epoxy material is roughtly formed to the desired degree of slope when it is in its uncured condition then it is cured and finally re-shaped to form the finished slope desired for a given embodiment of the invention. It will be understood that other suitable fluid deflecting means may be utilized to protect the shoulders 9 and 10 of the fuse carrier to prevent them from being subjected to excessive shear stresses by high pressure fluid impinging on their top surfaces. A further important feature of the novel fuse carrier of the present invention comprises a glass sleeve 26 that is embedded in the elongated portion 8 of the fuse carrier 7 adjacent the upper end thereof. As can be seen by referring t0 FIG. 2 of the drawing, a passageway 27 is formed through the body of epoxy material 28 disposed within the cylindrical center portion of the glass sleeve 26. Pursuant to the present invention, the glass sleeve 26 is embedded in the fuse carrier 7 during the molding operation that is used to form the fuse carrier, then the passageway 27 is formed through the center of the longitudinal axis of sleeve 26 to provide access for mounting pin 6 to be inserted therethrough so that it can support the fuse carrier 7 in its suspended position in pre-formed apertures on the support means 5a, as described above.

In operation, when high pressure liquid is circulated rapidly in the container 2 and through the apertures 23 of support means 5a to impinge on the shoulders 9 and 10 of fuse carrier 7, the upper end portion of the fuse carrier 7 is prevented from breaking in tension away from the rest of the fuse carrier by the force distributing effect of the glass sleeve 26, coupled with this sleeves relatively high tensile strength. Thus, with the combination of the strengthening effect of sleeve 26 and the uid pressure controlling streamlined surfaces 9m and 10a, it has been found that the interrupting rating of an oil filled cutout can be increased in excess of 50% above present safe ratings for a given size cutout, without increasing the probability of failure of the internal component parts of the cutout and without increasing the hazard of an explosion of the cutout. Accordingly, the safety of cutouts utilizing the present invention is substantially improved without adding appreciably to the cost of their manufacture. Utilizing the stress distributing principles inherent in the use of a sleeve such as glass sleeve 26, it will be apparent to those skilled in the art that some other high tensile strength sleeve materials will be suitable to practice this aspect of the invention with other embodiments thereof. However, after substantial testing the applicant has found that a glass sleeve affords opimum results when used with the low thermal coefficient of expansion epoxy fuse carrier 7 employed in the preferred embodiment of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The combination of a circuit interrupter having a container at least partially filled with insulating liuid, a fuse carrier, mounting means for mounting said fuse carrier in said container, a fuse supported by said fuse carrier beneath the surface of said insulating fluid, said fuse carrier comprising an elongated body portion of electrical insulating material having at least one shoulder portion projecting laterally therefrom with respect to the longitudinal axis of said body portion, at least one electrical Contact, means for mounting said contact on said shoulder adjacent said elongated body portion, and the improvement comprising streamlining means mounted on said fuse carrier between the body portion and said shoulder, said streamlining means being effective to substantially reduce the shear force transmitted to said shoulder by liquid that is forced to circulate under pressure in said container when said fuse fails and causes a substantial amount of arc-generated gas to be suddenly formed within the container.

2. The combination defined in claim 1 wherein said means for mo-unting said contact comprises means defining an aperture through said shoulder substantially parallel to the longitudinal axis of said fuse carrier and a threaded :bolt-like member releasably fastened in said aperture and connected to said contact, and said streamlining means comprises a body of moldable epoxy material that is shaped to form a sloped surface extending between said body portion and said shoulder, said surface being at an angle greater than 25 with respect to the longitudinal axis of said body portion, a portion of said body of moldable epoxy being disposed in said aperture to substantially fill the aperture above said bolt-like member.

3. The combination as defined in claim 1 including means defining an elongated passageway adjacent one end of said fuse carrier adapted to receive a pin therethrough, support means on the walls of said container adapted to receive the end of said pin when it is placed in operating position thereby to securely hold the fuse carrier in a predetermined position within said container, a glass sleeve means supporting said glass sleeve in intermittent contact with said fuse carrier with the longitudinal axis of said sleeve generally concentric with the longitudinal axis of said passageway.

4. The combination defined in claim 3 wherein said means for supporting said glass sleeve comprises a body of moldable epoxy material disposed within said sleeve and between said sleeve and the fuse carrier, said body of epoxy material within said sleeve forming the walls of said passageway through said sleeve.

S. The combination defined in claim 3` wherein said means supporting said sleeve comprises an integral portion of said body member formed closely around said sleeve thereby to eliminate all voids between said sleeve and said body member.

`6. The combination of a container at least partially filled with insulating fluid, a fuse carrier having an elongated body portion and a pair of contact supporting shoulders, support means in said container for supporting said fuse carrier in operative position therein, a fuse supported by said fuse carrier beneath the surface of said insulating fluid, a pair of electrical contacts respectively supported by said shoulders, means electrically connecting said fuse in series with said contacts, means defining passageways within said container through which said insulating `fiuid can circulate when said fuse fails and causes arc-generated gases to suddenly force the fluid to move within the container, said passageways being effective to cause fiuid circulating in the container to impinge on said shoulders thereby to stress the fuse carrier in a manner tending to shear the shoulders therefrom and to break the fuse carrier from said support means, the improvement comprising streamlining means defining a pair of integral surfaces of said fuse carrier extending respectively between said shoulders and the elongated body portion of `.said f-use carrier on the portions thereof adjacent where circulating fluid impinges on said shoulders, whereby said streamlining means is effective to substantially reduce the force of said circulating fluid tending to shear said shoulders from the :body portion of the fuse carrier.

7. The combination defined in claim 6- wherein said support means includes means defining a passageway through said fuse carrier adjacent one end thereof, a pin removably disposed in said passageway and supported in a fixed position by bracket means mounted on a wall of said container, and a glass sleeve imbedded in said fuse carrier with its walls surrounding said passageway.

8. Ay fluid-lled cutout having a fluid confining container, a fuse, and a fuse carrier having parts therein that are periodically subjected to mechanical stresses due to rapid movement of fluid in the container responsive to sudden formation of arc-generated gases in said container the improvement comprising, said fuse carrier composed of moldable epoxy material and shaped to have an elongated -body portion with a pair of shoulders projectingl laterally therefrom, a pair of contacts each respectively mounted on and supported in fixed positions by said shoulders, fluid defiecting means mounted on said fuse carrier and arranged to deflect fluid away from said shoulders thereby to prevent excessive shear forces being applied to said shoulders when the fluid in the container is moved rapidly by arc-generated gases.

9. An invention as defined in claim 8 wherein said fluid deflecting means comprise two bodies of epoxy material disposed respectively on each of said shoulders and shaped to define sloped surfaces that form angles greater than 30 with respect to the longitudinal axis 0f said fuse carrier thereby to defi'ect liuid that flows parallel to said fuse carrier away from the shoulders.

10. An invention as defined in claim 9 including a glass sleeve embedded in said fuse carrier adjacent one end thereof, means defining a passageway generally concentric with said sleeve and extending therethrough, fuse carrier supporting means extending through said passageway and coupled to a wall of said container to suspend the fuse carrier therefrom, said glass sleeve being effective to reinforce the fuse carrier and thereby prevent it from being broken by forces applied to said shoulders when fluid is moved rapidly in said container.

References Cited UNITED STATES PATENTS 1,203,316 10'/ 1916` -Downes 337-204 1,953,812 4/1934 Lincks 337--168 3,132,226 5/ 1964 Bennett 3337--168` HA'ROLD BROOME, Primary Examiner 

